Ultra-high Molecular Weight Polyethylene Materials Research Articles

Augmenting the mechanical performance of three‐dimensional woven composites by the synergistic effect of fabric architecture and interfacial interaction of carbon nanotubes

AbstractThree‐dimensional (3D) woven fabrics offer many advantages over planar woven fabrics for composite applications. Because of the complex structure of 3D woven fabrics, an in‐depth investigation is needed to understand the effects of fabric architecture and nanofillers on the mechanical and failure behavior of 3D woven composites. The present study investigates the effect of 3D woven ultrahigh‐molecular‐weight polyethylene (UHMWPE) orthogonal fabric architecture, with or without nanofillers, on the mechanical properties of composites. 3D woven orthogonal fabrics with varying proportions of stuffer‐to‐binder (S/B) yarns were manufactured and reinforced with an epoxy (EP) matrix. Multiwalled carbon nanotubes (MWCNTs) were infused as nanofillers to improve the interaction between the UHMWPE fabric and the EP matrix. 3D woven composite having an S/B ratio of 2:1 showed the maximum tensile strength and toughness. On the other hand, 3D woven composite with an S/B ratio of 4:1 showed higher flexural strength and impact resistance. The failure mechanism was also studied by examining the fractured surfaces of composites, which revealed matrix cracking, fiber pullout, predominant binder yarn failure, and yarn slippage. From this study, it is understood that for 3D fabric reinforcement, a balance between structural integrity and load‐bearing capacity of yarns is decisive, whereas for the matrix, the incorporation of MWCNTs is found to be advantageous.Highlights The role of structure of 3D woven orthogonal fabric on the mechanical behaviour of the UHMWPE‐epoxy composite is investigated. The addition of functionalized MWCNTs improves the tensile, flexural, and impact properties. The decisive role of the ratio of stuffer‐to‐binder yarns is established. Matrix cracking, debonding, and yarn failure are observed during tensile failure.

Optimization of soft armor: the response of homogenous and hybrid multi-ply para-aramid and ultra-high molecular weight polyethylene fabrics under ballistic impact

This research investigated the ballistic response of homogenous and hybrid multi-ply fabrics toward developing a full-scale hybridized soft armor system. Fabrics with varying yarn and thread counts were manufactured from para-aramid and ultra-high molecular weight polyethylene yarns through a plain-woven architecture. Homogeneous fabrics used the same yarn and thread count for two- and three-ply systems. For hybrid systems, two- and three-ply stacks were assembled in various sequences including increasing and decreasing cover factor ( Cfab) and varying yarn types as the strike face and rear face. Ballistic impact testing was performed on all fabrics at low (340 m s−1) and high velocity (620 m s−1). Observations and measurements were performed to determine failure mechanisms, energy absorption, transverse wave propagation, and system effects of multi-ply systems. Hybrid systems showed significant differences in specific energy absorbed (SEA), dependent on the layer order. The para-aramid hybrid systems impacted at 340 m·s−1 showed a significantly greater SEA when the fabrics were ordered with an increasing rather than a decreasing cover factor. At 620 m·s−1 the difference in SEA was less pronounced or absent entirely. It was concluded that hybridization would enhance the performance of a soft armor system and was likely to be most effective for the rear layers of the system where fabrics with a progressively increasing cover factor that were manufactured of fine (550 dTex) para-aramid yarns would offer an advantage. The front layers of the system, subjected to higher strain loading, would benefit from low cover factor fabrics (0.76), which maximize the dissipation of strain from the point of impact.

Impact-Protective Bicontinuous Hydrogel/Ultrahigh-Molecular Weight Polyethylene Fabric Composite with Multiscale Energy Dissipation Structures for Soft Body Armor.

Soft body armor greatly improves the comfort and security of the wearers. Although laminates based on high-performance fabrics have been adopted, it remains an enormous challenge to develop fabric laminates having flexibility, low bulge deformation, and ballistic protection capability simultaneously. Herein, we report a bullet-proof bicontinuous hydrogel (BH)/ultrahigh-molecular weight polyethylene fabric (UPF) composite. The presence of the BH significantly improves the impact resistance performance of the UPF, without compromising its flexibility. In specific, the multiscale energy dissipation structures composed of hydrogen bond associations in the chain scale, bicontinuous phase structures in the nanoscale, and fibers in the microscale are broken to dissipate energy. As a result, the impact energy of the bullet is greatly absorbed and the bulge height of the composites is significantly reduced in contrast to the neat UPF laminates. This study indicates that the flexible BH-UPF composites with multiscale energy dissipation structures have a promising application in soft body armor.

Enchanching Body Armor: Evaluating UHMWPE with Contoured Surfaces for Improved Anti-Ballistic Performance using Finite Element Methods

Anti-ballistic is an indispensable personal protective equipment such as body armour for military and police personnel. This tool has received a lot of attention in recent decades due to increasing threats and insurgencies. Several studies have reviewed the development of anti-ballistic technology. However, there still needs to be discussion related to the development of anti-ballistics using UHMWPE (Ultra High Molecular Weight Polyethylene) and the contours of the surface of the UHMWPE. In addition, anti-ballistic studies are rarely carried out compared to other fields. This is because discussions or research related to weapons are still sensitive discussions. This study aims to determine whether the quality of body armour made using UHMWPE which one of the surfaces is given a specific profile, is better when compared to UHMWPE, which has no contours on all surfaces. UHMWPE material that is given a certain profile is one of the ideas chosen because it has high strength and aesthetic value, so it is expected to withstand bullet impact, comfortable and attractive when used. The antiballistic properties of UHMWPE given the diamond contour were obtained from numerical simulations using the finite element model (explicit dynamics) of ANSYS Workbench software. The two UHMWPE variants used in the multiplelayered configuration consist of UD UHMWPE sheets. Ballistic testing used a 7,62 mm calibre lead bullet with a velocity of 720 m/s. The material model of the bullet and UHMWPE plate used the Johnson-Cook plasticity model.

Mechanical properties of interlayer hybrid textile composite materials based on modified aramid and UHMWPE fabrics

AbstractAramid fibers and ultra‐high molecular weight polyethylene (UHMWPE) fibers lack active surface functional groups, and the surface is smooth, limiting their practical application in textile composite materials. In this study, zinc oxide nanorods were used to grow on aramid fibers surfaces, and oxygen plasma followed by treatment with a silane coupling agent was used to modify UHMWPE fibers. The effects of surface modification on the surface morphology and composition, and mechanical properties of fibers and composites were investigated. The mechanical response of interlayer hybrid textile composite materials based on modified aramid and UHMWPE fabrics was examined. The results reveal that surface roughness, active surface functional groups, and wettability that can be controlled by treatment conditions and parameters are important for improving interface adhesion. In addition, the interlayer hybridization pattern as a result of using dissimilar layer materials and altering stacking sequence has a great impact on the mechanical behavior of hybrid textile composite materials.

Validation of a biomechanical testing protocol of craniodorsal hip luxation in feline cadavers and comparison of two ultra-high molecular weight polyethylene materials used for extra-articular hip stabilisation.

The aim of our study was to describe a biomechanical testing protocol to reproduce ex vivo craniodorsal hip luxation specific to the feline model, and evaluate the biomechanical properties of an intact hip joint compared with the fixation strength of two different techniques of extra-articular hip stabilisation. Eighteen hip joints (femur and hemipelvis) were harvested from nine mature feline cadavers. CT was performed for each hip joint so that a biomechanical base specific to each joint morphotype could be created using computer-aided design. The biomechanical bases were then produced using a three-dimensional printer to secure the hip joints during testing. A total of 34 biomechanical compression tests were performed. Eighteen compression tests were performed in the control group, of which two fractured. The remaining 16 hip joints were then randomly assigned either to group A (hip joints stabilised with an extra-articular ultra-high molecular weight polyethylene (UHMWPE) implant secured by an interference screw [n = 8]) or to group B (hip joints stabilised with a UHMWPE iliofemoral suture [n = 8]). Mean ± SD yield, failure load and linear stiffness in the control group were 616 ± 168 N, 666 ± 158 N and 231 ± 50 N/mm, respectively. The relative fixation strength (% of intact joint) before hip luxation in groups A and B was 43.8% and 34.7%, respectively. No statistical difference was found between groups A and B for yield and failure load. However, the reoccurrence of craniodorsal hip luxation was higher in group B than in group A, in 5/8 and 0/8 tests, respectively. Moreover, in group A, the extra-articular UHMWPE implant induced caudodorsal hip luxation, reported as failure mode in 7/8 cases. This modified biomechanical protocol for testing craniodorsal hip luxation in a feline model was validated as repeatable and with acceptable variance. The extra-articular UHMWPE implant stabilisation technique proved to be more efficient in avoiding reoccurrence of craniodorsal hip luxation than UHMWPE iliofemoral suture.

Injection‐Molded Ultrahigh Molecular Weight Polyethylene Material with Improved Moldability for Artificial Joint Implants Design

Fabrication of pure ultrahigh molecular weight polyethylene (UHMWPE)‐based artificial joint implants is a bottleneck problem as it is only limited to quasistatic approaches that have low efficiency due to the high density of fusion defects. The main objective of this work is to improve the moldability of UHMWPE using the injection molding technique while maintaining its superior mechanical integrity. Groups of UHMWPE samples are injected at barrel melting temperatures of 300, 320, 340, and 360 °C, at various injecting pressures. The high‐temperature melting (HTM) allows the fabrication of robust UHMWPE samples using injection molding with an improved yield stress of 29.63 ± 3.19, compared to 23.0 ± 0.6 and 17.8 ± 0.75 achieved by HTM compression molding and conventional compression molding, respectively. Moreover, the scanning electron microscopy (SEM) results suggest an almost complete elimination of all fusion defects, and that is supported by the outstanding tensile strain at breaks reaching up to approximately 1300%. The thermochemical properties of the injection‐molded UHMWPE samples are tested as well to investigate the impact of HTM on their characteristics. Moreover, the materials’ biocompatibility and wear are assessed. This study sets up a new approach to fabricate high‐performance injection‐molded UHMWPE joint implants by HTM.

Probing lubricated sliding wear properties of HDPE/UHMWPE hybrid bionanocomposite.

Ultra-high molecular weight polyethylene (UHMWPE) and its derivatives have been clinically used as an acetabular liner material in total hip joint replacement (THR) over last six decades. Despite significant efforts, the longevity of UHMWPE implants is still impaired due to their compromised tribological performance, leading to osteolysis and aseptic loosening. The present study aims to critically evaluate and analyze the tribological performance, of the next generation acetabular liner material, that is, a chemically modified graphene oxide (GO) reinforced HDPE/UHMWPE (HU) bionanocomposite (HUmGO), against stainless steel (SS 316L) counterface in lubricated conditions. This work also provides a performance comparative assessment of HUmGO with respect to medical grades, UHMWPE (UC) and crosslinked UHMWPE (XL-UC). Significant attempts have been made to correlate the tribological properties (frictional behavior, wear rate, wear debris shape and size, wear mechanism) with the physicomechanical conditions (contact stresses) at sliding contact and the variation in molecular architecture of different UHMWPE materials. Additionally, an emphasis is put forward to critically anlyze the nature of lubrication regime based on the bearing characterstic parameters. HUmGO exhibited a lower COF (0.07) and specific wear rate (2.86 × 10-8mm3/Nm) than UC and XL-UC under identical sliding conditions. The worn surfaces on HUmGO revealed the signatures of less abrasive wear and limited deformation. Based on the estimated lambda (λ) ratio and Sommerfield number, all the investigated sliding contacts exhibited boundary lubrication. Taken together, the modified GO reinforced HDPE/UHMWPE bionanocomposite can be considered as a new generation biomaterial for the fabrication of acetabular liner for hip-joint prosthesis.

Tresca stress evaluation of Metal-on-UHMWPE total hip arthroplasty during peak loading from normal walking activity

Ultra-High Molecular Weight Polyethylene (UHMWPE) is one of the most widely used biomaterials for applications in the field of medical devices, especially implants. The use of these materials together with metal is widely used for the combination of materials in total hip arthroplasty as hard-on-soft. Although the use of this combination of materials has been widely adopted, the long-term adverse effects of UHMWPE are a concern for implant users. The selection of the right metal material as a UHMWPE counterpart is crucial to minimize the risk to the patient. Three types of metal materials, namely Cobalt Chromium Molybdenum (CoCrMo), Stainless Steel 316L (SS 316L), and Titanium Alloy (Ti6Al4V) were evaluated using Tresca stress. The computational simulation was chosen with a two-dimensional model using the highest load in normal walking activities as the loading condition. The results show that the combination of materials on CoCrMo-on-UHMWPE bearings gives a Tresca stress value of 7.595 MPa, which is the lowest when compared to the other two combinations of metal and UHMWPE materials.

Influence of Topical Cross-Linking on Mechanical and Ballistic Performance of a Woven Ultra-High-Molecular-Weight Polyethylene Fabric Used in Soft Body Armor

We demonstrate that topical cross-linking of woven ultra-high molecular weight polyethylene (UHMWPE) fabric with a small-molecule bis-diazirine reagent can enhance the fabric’s resistance to tear and perforation and could provide a lead to further increase the protection provided by a soft body armor made from UHMWPE materials. A series of experiments confirms that the enhancement is likely due to cross-links formed within and between the yarns constituting the woven fabric and that cross-linking particularly strengthens the fabric along its bias direction. The treated fabric was incorporated into multilayer composite panels and challenged in ballistic tests. These measurements revealed that as low as a 1 wt % cross-linker can significantly increase the V50 ballistic limit by 18 m/s.

Developing thermoplastic hybrid titanium composite laminates (HTCLS) at room temperature: Low-velocity impact analyses

Hybrid titanium composite laminates (HTCLs) are high-performance light-weight fiber metal laminates (FMLs) that are being increasingly used in various industries such as aeronautical, military, and marine thanks to their optimized fracture toughness, impact resistance, and thermal performance. In the current study, the low-velocity impact (LVI) characteristics of a new generation of thermoplastic (TP) HTCLs at various energy levels are investigated. To do so, Ti-6Al-4 V sheets, carbon fabrics, and ultra-high molecular weight polyethylene (UHMWPE) fabrics are used to fabricate multiple laminates with different fiber types, metal volume fractions, and lamination layups. A low-cost resin infusion process is employed for manufacturing the laminates at room temperature by using a novel liquid thermoplastic methyl methacrylate resin, Elium® 188. Before fabrication, a multi-step surface treatment method is applied on Ti alloy sheets to enhance the interfacial properties between the composite layer and the metal alloy sheet. In addition to TP-HTCLs, equivalent thermosetting (TS) HTCLs with an epoxy resin, Epolam, are fabricated to compare the results and evaluate the possibility of fabricating recyclable TP-FMLs at room temperature with enhanced out-of-plane properties. Impact properties including contact force, deflection, energy parameters, and related damage modes are investigated and presented for each laminate. It is concluded that the newly developed TP-HTCLs can be cured at room temperature and have enhanced impact properties compared to those of TS-HTCLs. Besides, the HTCL with UHMWPE fabrics on its composite sides (before the Ti alloy sheets) performs better in LVI compared to that with carbon fibers on the top and bottom (of its composite core) since UHMWPE exhibits higher strain to failure and fracture toughness compared to carbon fibers.

Use of Artificial Neural Networks to Optimize Stacking Sequence in UHMWPE Protections.

The aim of the present work is to provide a methodology to evaluate the influence of stacking sequence on the ballistic performance of ultra-high molecular weight polyethylene (UHMWPE) protections. The proposed methodology is based on the combination of experimental tests, numerical modelling, and Artificial Neural Networks (ANN). High-velocity impact experimental tests were conducted to validate the numerical model. The validated Finite Element Method (FEM) model was used to provide data to train and to validate the ANN. Finally, the ANN was used to find the best stacking sequence combining layers of three UHMWPE materials with different qualities. The results showed that the three UHMWPE materials can be properly combined to provide a solution with a better ballistic performance than using only the material with highest quality. These results imply that costs can be reduced increasing the ballistic limit of the UHMWPE protections. When the weight ratios of the three materials remain constant, the optimal results occur when the highest-performance material is placed in the back face. Furthermore, ANN simulation showed that the optimal results occur when the weight ratio of the highest-performance material is 79.2%.

Optimization of soft armor: the response of single-ply para-aramid and ultra-high molecular weight polyethylene fabrics under ballistic impact

Typical soft armor systems are constructed of multiple layers of a single fabric type. This empirical research sought to begin optimization of these systems through hybridization, sequencing dissimilar armor fabrics to maximize their ballistic protective performance, by first investigating single plies with a spectrum of properties to determine their behavior and response to impact. Eight individual plain weave fabrics with varying yarns and thread counts were manufactured from para-aramid and ultra-high molecular weight polyethylene (UHMWPE) yarns and physical and ballistic characterizations were conducted. The ballistic impact tests established the specific energy absorption (SEA) of each fabric across a range of impact velocities (340–620 m·s–1) and the transverse displacement wave velocity across the rear of the fabric was found using digital image correlation. Low cover factor ( Cfab) fabrics (0.74–0.84) consistently showed faster transverse wave speed than the high Cfab fabrics (0.84–0.96) for any given yarn type. The relative SEA of the fabrics varied dependent on both the impact velocity and number of plies impacted. It was found that lower Cfab fabrics had the highest SEA, critical velocity and transverse wave velocity. UHMWPE fabrics were not considered suitable for a woven hybrid system as they had a significantly lower SEA compared to all the para-aramid fabrics. Results indicate that a hybrid system, when considered as a theoretical spaced system, would benefit from higher Cfab fabrics as rearward layers. However, transverse wave results suggest the lower response of these fabrics may inhibit lower Cfab fabrics at the front of a combined hybridized system.

Effect of structural parameters on the cut resistance of para-aramid and ultra-high molecular weight polyethylene weft knitted fabrics

In this study, the cut resistance of pure and hybrid knitted para-aramid and ultra-high molecular weight polyethylene fabrics with different structural parameters were measured according to ASTM F1790. The results showed that there is an optimum value for stitch density in which the cut resistance is maximized. The highest and the lowest cut resistance was observed in the courses and the wales directions, respectively. The interposed values were obtained in the bias direction. Coating with casting polyurethane resin increased the cut resistance of the fabrics. Para-aramid samples had higher cut resistance than UHMWPE samples in higher stitch densities, and hybrid samples showed a higher cut resistance than the pure ones, due to some of their structural features.

Mechanical and Cytocompatibility Evaluation of UHMWPE/PCL/Bioglass® Fibrous Composite for Acetabular Labrum Implant.

In this study, a fibrous composite was developed as synthetic graft for labral reconstruction treatment, comprised of ultra-high molecular weight polyethylene (UHMWPE) fabric, ultrafine fibre of polycaprolactone (PCL), and 45S5 Bioglass®. This experiment aimed to examine the mechanical performance and cytocompatibility of the composite. Electrospinning and a slurry dipping technique were applied for composite fabrication. To assess the mechanical performance of UHMWPE, tensile cyclic loading test was carried out. Meanwhile, cytocompatibility of the composite on fibroblastic cells was examined through a viability assay, as well as SEM images to observe cell attachment and proliferation. The mechanical test showed that the UHMWPE fabric had a mean displacement of 1.038 mm after 600 cycles, approximately 4.5 times greater resistance compared to that of natural labrum, based on data obtained from literature. A viability assay demonstrated the predominant occupation of live cells on the material surface, suggesting that the composite was able to provide a viable environment for cell growth. Meanwhile, SEM images exhibited cell adhesion and the formation of cell colonies on the material surface. These results indicated that the UHMWPE/PCL/Bioglass® composite could be a promising material for labrum implants.

Macrophage inhibits the osteogenesis of fibroblasts in ultrahigh molecular weight polyethylene (UHMWPE) wear particle-induced osteolysis

BackgroundIn the ultrahigh molecular weight polyethylene (UHMWPE) prosthetic environment, fibroblasts affected by wear particles have the capacity of osteogenesis to reduce osteolysis. We aimed to assess the effects of macrophages on the osteogenic capability of fibroblasts treated with UHMWPE wear particles.MethodsThe effect of different concentrations of UHMWPE (0, 0.01, 0.1, and 1 mg/ml, respectively) on macrophage proliferation were validated by MTT assay to determine the optimum one. The fibroblasts viability was further determined in the co-culture system of UHMWPE particles and macrophage supernatants. The experiment was designed as seven groups: (A) fibroblasts only; (B) fibroblasts + 1 mg/ml UHMWPE particles; and (C1–C5) fibroblasts + 1/16, 1/8, 1/4, 1/2, and 1/1 supernatants of macrophage cultures stimulated by 1 mg/ml UHMWPE particles vs. fibroblast complete media, respectively. Alizarin red staining was used to detect calcium accumulation. The expression levels of osteogenic proteins were detected by Western blot and ELISA, including alkaline phosphatase (ALP) and osteocalcin (OCN).ResultsThe concentration of 0.1 mg/ml was considered as the optimum concentration for macrophage proliferation due to the survival rate and was highest among the four concentrations. Fibroblast viability was better in the group of fibroblasts + 1/16 ratio of macrophage supernatants stimulated by 1 mg/ml of UHMWPE particles than the other groups (1:8, 1:4, 1:2, 1:1). ALP and OCN expressions were significantly decreased in the group of fibroblasts + 1/4, 1/2, and 1/1 supernatants stimulated by 1 mg/ml of UHMWPE particles compared with other groups (1/8, 1/16) and the group of fibroblasts + 1 mg/ml UHMWPE (p < 0.5).ConclusionsMacrophages are potentially involved in the periprosthetic osteolysis by reducing the osteogenic capability of fibroblasts treated with wear particles generated from UHMWPE materials in total hip arthroplasty.

Natural fiber-reinforced high-density polyethylene composite hybridized with ultra-high molecular weight polyethylene

A great deal of research and development work has been recently conducted on natural fiber-reinforced polymer matrix composite for its abundancy, low density, excellent damping characteristic, and good mechanical properties. However, the low strength of natural fiber composite has limited its use to only low stress applications. The purpose of this work is to develop a natural fiber hybrid material with both enhanced strength and failure strain using a novel approach and study the effect of the processing temperature on its microstructure and performance. High-strength ultra-high molecular weight polyethylene fabrics are co-molded onto the surfaces of a kenaf fiber high-density polyethylene-based composite material by single-step compression molding. The status of the ultra-high molecular weight polyethylene fabrics at different processing temperatures is investigated using microscopic analysis. The tensile strength and impact strength of the hybrid material are evaluated. It is found that its tensile strength is increased by more than 90% with only 8% ultra-high molecular weight polyethylene fiber reinforcement added and its low density is maintained.

Preparation, characterization and properties of shear thickening fluid impregnated fabric composites

Shear thickening is a non-Newtonian flow behavior characterized by the increase of viscosity with the increase in applied shear rate. Due to this remarkable property of shear thickening fluid (STF), it has received extensively attention in armor protection fields. Through a process of impregnation, the STF in body armor has allowed further enhancement without hindering the flexibility of fabrics, which has led to the development of the concept of liquid body armor. In this paper, the STFs were prepared by mechanical stirring of silica nanoparticles dispersed in liquid polyethylene glycol. The rheological properties of as-prepared STFs were tested. Aramid and ultra-high molecular weight polyethylene fabrics were soaked in STF/ethanol solution to make STF/fabric composites. Knife quasi-static penetration tests were performed on the neat fabrics and STF/fabric composite targets for engineered knife on areal density basis. The results showed that compared with the neat fabrics, the STF impregnated fabrics exhibited better penetration resistance without affecting the fabric flexibility.

Initial response of human bone marrow–derived stem cells after contact with ultrahigh-molecular-weight polyethylene (UHMWPE) material: An in vitro study on cell viability and interleukin-6 expression

Introduction:Ultrahigh-molecular-weight polyethylene (UHMWPE) is a thermoplastic polymer useful in biomaterial applications, especially in orthopedic field. Yet, little is known concerning its initial effect on human bone marrow stem cells (hBMSCs) after implantation.Materials and Methods:A cytotoxicity analysis was performed with a 3-(4,5-dimethylthiazol 2-yl)-2,5-diphenyltetrazolium assay after 24, 48, and 72h of incubation of hBMSC culture. Expression of interleukin-6 (IL-6) was measured using enzyme-linked immunosorbent assay. Cell viability was measured with Inhibitory concentration 50% (IC50) formula.Results:All treatment groups showed a cell viability of >50% ranging from 78% to >100%. Lower expression of IL-6 of hBMSC compared to control group was found in 48h of incubation period.Conclusion:hBMSC showed high cell viability after initial contact with UHMWPE material. Modulation of IL-6 expression was present at the initial stage as a response to foreign material.

A Micro Constitutive Model for Ultra-High Molecular Weight Polyethylene Orthopaedic Implant Bearings

Ultra-high molecular weight polyethylene (UHMWPE) is a tough semi-crystalline polymer employed widely as a bearing material in total joint replacements. The micromechanical model has been presented that predicts stiffness of UHMWPE as an aggregate of crystalline inclusions (lamellae) embedded in a rubbery matrix of amorphous polymer chains. The differential scheme was chosen for its ability to represent the interaction between an inclusion and the matrix. Numerical simulations show that increasing lamellar thickness results in less stiffness, less shear stress imposed on the lamellae, indicates that thick lamellae are desirable for UHMWPE materials utilized in total joint replacement bearings.